This invention relates to a subsea flange connection used in the offshore oil and gas industry for connecting joints in a riser string or other components, for example, the connection may be used in other subsea components (e.g. pipelines).
Risers and flowlines consist of sections of pipe that need to be secured together to form a contiguous pipe. Accordingly, the securement between the different pipe sections needs to be strong and reliable. The sections of pipe are often provided with flanges to enable the pipe section to be easily secured together. Each flange may include securement apertures radially spaced around the flanges. Corresponding securing nuts and bolts may then be used to secure the flanges together. Each pair of nut and bolt requires the nuts to be rotated multiple times in order to tighten the securement and provide an effective connection between the two sections of pipe. However, since each connection includes several pairs of nuts and bolts and each requires several or numerous rotations to effect the tightening, the time taken to effectively join the pipes can be relatively long. This is known as bolt torquing. An alternative method comprises bolt tensioning which involves initially stretching a threaded bar or stud and then winding down the nut (which can be done by hand). However, this method is slow as each stud needs to be stretched independently, requiring installing and removal of the tools from each stud thread. Since the riser cannot be used whilst the sections are being connected, this can be an expensive operation.
Similar flanged connections are used on subsea equipment; however, the number of components and complexity of motion typically precludes the use of robotic vehicles, so these connections are typically restricted to depths that divers can access. Subsea robotic connections are typically achieved with clamp hub connectors. However, this application is limited by the load and fatigue capacity which is often significantly reduced compared to a flanged connection.
It is an aim of the present invention to overcome at least one problem associated with the prior art whether referred to herein or otherwise.